1. Chapter 15 Evolution

2. What is evolution? Change in a population over time
Changes occur at genetic level
 mutations

3. Mutations
Change in the DNA code
Can affect traits / phenotype

4. The Darwin Dude? 5 year voyage on Beagle (1831-36)
Naturalist: surveyed coast of S.A.
Wrote “Origin of Species”

5. Galapagos Island Facts
Part of Ecuador
13 main volcanic islands
Formed between MYA

6. Darwin & Galapagos Organisms adapted to their environment
“Darwin’s Finches”
Mechanism for evolution = Natural Selection

7. Noteworthy Species

8. Darwin’s Finches Adaptive Morphology

9. Why do species change?
Variations & adaptations help organisms survive

11. Camouflage

12. Camouflage

13. Natural Selection Organisms with favorable traits survive & reproduce
Variation is key

14. Natural Selection (cont.)
Struggle for existence
Species become better fit for their environment

15. Natural Selection (cont.)
4 Main Principles (pg 421):
Variation
Heritability
Overproduction
Reproductive Advantage

17. Types of Natural Selection
1. Stabilizing Selection: Average phenotype favored
Ex. Human baby weight

18. Stabilizing Selection

19. Types of Natural Selection
2. Directional Selection: increases “extreme” versions of traits
Ex. Peppered Moth, Darwin’s finches

20. Peppered Moth: Natural Selection

21. Directional Selection

22. Types of Natural Selection
3. Disruptive Selection: splits populations into 2 groups
Both extremes favored
Ex. Marine & Land Iguanas

23. Disruptive Selection

24. Evidence of Evolution Fossil Record Fossils: preserved evidence
Found in Sedimentary rock

25. “Soft parts” don’t fossilize
Fossil Record (cont)
“Soft parts” don’t fossilize
Specific conditions needed to form fossils
Lack of “transitional” fossils

27. Evidence of Evolution 2. Homologous Structures:
Anatomically similar structures
Evidence of common evolutionary origin

28. Homologous Structures

31. Evidence of Evolution 3.Comparative Embryology:
similarities in embryos

34. Evidence of Evolution
4.Compararative Biochemistry: Organisms have similar DNA, genes and enzymes

36. Evidence of Evolution 5. Vestigial Structures:
reduced in size, no longer have function

38. What is Speciation? Formation of new species
Become genetically different

39. What are Species?
Group of organisms that can interbreed & produce fertile offspring

40. Infertile Species
Horse + Donkey = Mule

41. Liger

42. Species Loop Hole Not a perfect definition Used for classification
Some different species can produce fertile offspring

43. Rate of Speciation Gradualism: Evolution occurring at slow rate
Punctuated Equilibrium: Evolution occurring at irregular rates

45. Cause of Speciation Geographic Barriers Environment Changes
Mountains, Rivers, etc.
Environment Changes